Advances in Electrode Materials for Rechargeable Batteries

Relaxed targeting rules allow PIWI-clade Argonaute proteins to silence ever-mutating transposons

“…GTSF1 has been proposed to stabilize the catalytically competent geometry between the target and the PIWI catalytic center ( 33 ). For AGO proteins, perfect pairing between an siRNA and its target moves target nucleotides t10 and t11 into the endonuclease active site.…”

“…Unlike siRNA-directed, AGO-catalyzed transcript cleavage, target slicing by PIWI proteins requires the auxiliary factor GTSF1/Asterix ( 33 ). GTSF1 accelerates ~10–100-fold the otherwise slow target cleavage by PIWIs, likely by stabilizing the catalytically competent conformation of PIWI proteins ( 33 ). Why PIWI slicing evolved to require an auxiliary protein is unknown.…”

“…S2A). Moreover, MILI and MIWI, directed by 21-nt guides, cleave targets as efficiently as when loaded with full-length piRNAs ( 33 ). Nonetheless, we find that extending pairing beyond piRNA nucleotide g20 allows PIWI proteins to tolerate guide:target mismatches.…”

“…We incubated the target RNA library with either purified MILI or MIWI loaded with a 5’ monophosphorylated synthetic RNA (26 nt for MILI, 30 nt for MIWI; fig. S1B) ( 33 ) and isolated and sequenced RNAs bound to the piRNA•PIWI-protein complex (piRISC). The sequencing data was analyzed using an approach that estimates the affinity ( K D ) of piRISC for each binding-site type ( 39 ).…”

“…The modal length of piRNAs is 5–10 nt longer than that of siRNAs (26–31 nt vs ~21 nt) ( 4, 42–45 ), yet PIWI proteins do not require pairing to these additional 3’ nucleotides to cleave a target RNA ( 22, 33, 41 ). In vitro, 16–21-nt long contiguous complementarity sufficed for MILI and MIWI to reach their maximum endonuclease rate (fig.…”